You'll probably won't get much more response on this site than 'look in your crystal ball' because you're question is not very good.
Obviously I was wrong since while typing there was a better answer *grin*. Still I think that my claim holds...)
Before you post you should at least have some kind of vision what your programm shall do and what it will be coded like. What I am trying to say is that the Monks around here can't teach you programming, we can just help you with sub-problems and review the code you already have.
So, you'll probably want to read the documentation to 2 of the major perl standard modules: CGI and Date::Calc. If you do a search here you'll find LOTS of ressources to this concern.
you begin bashing the string with a +42 regexp of confusion